Process for the treatment of synthetic threads



NN "WQ Dec. 27, 1955 B. .1. BLoMBl-:RG

PROCESS FOR THE TREATMENT OF SYNTHETIC THREADS Filed NOV. 20, 1950 INVENTOR ATTORNEY 2,728,629 Patented Dec. 27, 1955 PROCESS FOR THE TREATMENT OF SYNTHETIC THREADS Barend Jan Blomberg, Velp, Netherlands, assignor to American Enka Corporation, Enka, N. C., a corporation of Delaware Application November 20, 1950, Serial No. 196,689

Claims priority, application Netherlands December 13, 1949 3 Claims. (Cl. 3-.151.2)

This invention relates to an improved process for the treatment of synthetic threads, and more particularly to a continuous liquid treatment of a linearly moving sheet of spaced parallel threads within an open receptacle.

According to one type of continuous spinning in the production of synthetic threads, e. g., viscose threads, a viscose solution is forced through a plurality of spinnerets into a common coagulating bath and the thus freshly formed threads are conducted to aftertreatment baths for further regeneration, purification, finishing and drying, all as one continuous operation. One of the most practical and economical methods of effecting these aftertreatments is to pass the threads in parallel, in what is commonly referred to as sheets, through open troughs or receptacles, containing the required treating liquids.

Many various embodiments of this type of treating apparatus are well known in the art, and for most purposes the systems now in use function satisfactorily. The same general system is disclosed in U. S. Heim Patent No. 2,334,325 and refinements and improvements thereon are described and claimed in U. S. application Serial No. 182,534 now Patent No. 2,566,438.

One system in which the present invention is particularly applicable is disclosed in French Patent No. 884,700. As shown in that patent, a sheet of threads is guided through a series of aftertreatment baths in a substantially horizontal direction near the surface of the liquid, the threads being in parallel only a few millimeters apart. This process is very simple, is easily supervised, and the apparatus is cheap to install and maintain. These freshly spun viscose threads are much more sensitive to the conditions of treatment in the various liquid receptacles than threads which have already been completely formed. That this is true can be seen by the emphasis placed in the patent literature dealing with such systems upon the necessity for controlling the tension, friction, and path of the thread travel through the various baths.

There are several conditions that are generally encountered when the sheet of threads is conducted through various liquid receptacles. First, since the chemical reactions that take place, such as regeneration and desul furization, do not occur instantaneously, long thread paths are required. As thread speeds are raised, thread travel distances must be increased proportionately in order to maintain the same treatment time. Also, in practice the receptacles are usually designed to hold a fairly substantial volume of treating liquid in order that both the liquid temperature and concentration will remain relatively constant. Furthermore, for reasons of economy, the spacing between successive threads is usually kept to an absolute minimum, while the sheet of threads is usually guided immediately underneath the level, and near the surface of the liquid in the treating receptacle in order to reduce to a minimum the number of changes of thread direction and facilitate the threading-up and maintenance operations.

the liquid surface of a long shallow receptacle containing a large volume of liquid, an undesirable wave formation on the liquid surface is inevitably obtained, which is especially pronounced for the heavier thread deniers (i. e. 1100 and greater) and the higher thread speeds (60-100 meters per minute). The sheet of closely spaced threads moving through the trough exerts a substantial friction effect, not only upon the liquid layers immediately surrounding the threads, but also upon the whole contents of the trough, particularly if shallow troughs are used, with the result that the liquid accumulates at the thread-exit end of the receptacle and the liquid level falls at the inlet end. When the hydrostatic pressure predominates at the exit end the liquid is pushed back against the friction of the moving threads, and a wave is formed. The threads then start to build up another difference in liquid level, and the action becomes repetitive.

This effect is enhanced with a counter-current flow of treating liquid through the receptacle, for in addition to the liquid carried to the thread-exit end by the threads themselves, the inilux of fresh liquid at the same end and the removal of liquid at the opposite end increases the rate of growth of liquid level difference.

This wave motion is undesirable, especially in the manufacture of viscose rayon threads, for several reasons. First of all, the waves produce variations in the thread tension and stretch, thereby introducing a non-uniformity of treating conditions. Also, a non-uniform mixing of treating liquids is produced, especially with counter-current flow, which gives rise to a further non-uniformity of treating conditions. Finally, when liquid is admitted or removed at the ends of the receptacles, a regular rate of supply and discharge is rendered impossible.

l't is therefore an object of this invention to provide an improved method for the continuous liquid treatment of a plurality or sheet of moving spaced parallel threads in an open receptacle.

lt is contemplated, according to this invention, to add to the open receptacle a wave damping material of such a shape that it possesses a large surface area relative to its volume but also has suicient openings to permit the ready although tortuous flow of liquid therethrough.

Another object of this invention is to treat a plurality of moving spaced parallel threads in an open receptacle containing a liquid whose surface is less turbulent and freer from wave motion than heretofore has been possible.

lt is a still further object of this invention to provide an improved method for the continuous liquid after-treatment of a plurality of spaced parallel freshly spun viscose rayon threads moving in a horizontal direction near the surface of the liquid within an open receptacle.

Other objects and advantages of this invention will become apparent from the following detailed description thereof, when considered in conjunction with the accompanying drawings, wherein:

Figure l is a longitudinal view in vertical section of one open receptacle constructed in accordance with this invention; and

Figure 2 is a view in transverse section taken on line 2-2 of Figure l.

Referring more particularly to the drawings, a at sheet of parallel threads 10 is shown passing linearly in a horizontal direction through an open receptacle gen- However, with a sheet of threads travelling just under erally indicated at 11. This receptacle 11 is composed of two side walls 12, a front end wall 13, a rear end wall 14 and a bottom 15. The receptacle 11 is open at its top to permit free access at both sides thereof.

As the threads 10 are guided in parallel relation to the receptacle 11, they pass over the top edge 16 of the front end wall 13, the edge 16 being rounded off and polished to minimize the friction between the edge 16 and the threads 10 passing thereover.

3 in order to elfect optimum liquid treating conditions as the threads it) pass through bath 17, a series of guiding rods it? and l? are removablyl attached to the side walis i2 or receptacle 11 so that they extend in a direction transverse to the direction of thread travel. The guiding rods 1*? function to support the threads it) in a horizontal manner and preventY them from sagging and coming ,in Contact with a wave damping material 2d to be hereinafter more fully described. The guiding rods 18 act to press therthreads into contact with the bath 17 at, or just below, the surface thereof.

'e Rear end wall i4 is rounded and polished on its top edge 21 in the same manner as the top edge 16 of front end wall 13. As an alternative, combs may be used in lieu of the thread guiding edges 16 and 21. Polished edge 21 permits the threads if' to leave the bath with a minimum of friction and be in readiness for further aftertreatments in similarly constructed receptacles or for drying and collecting.

A spillway 22 is provided adjacent and parallel to rear end wallV 14. The top edge 23 of this spillway 22 is about even with the horizontal plane formed between guiding rods 1S and 19. This maintains a liquid level of the bath 17 just above the horizontal path of threads it). Bath 17 is continuously circulated by pumping the same into conduit 24 and withdrawing it through conduit 25 as it overflows spillway 22. However, if counter-current treatment is required, the adit and exit conduits can be reversed.

The receptacle 11 is substantially iilled with a wave damping material 20 mentioned above which can consist of a variety of substances as long as they are suiciently corrosion resistant. Moreover, they should have a large surface area in proportion to the volume they occupy while readily permitting the tortuous liow of liquid through the mass of particles. Filling materials that fultill these qualifications and are particularly well suited for the purpose of inhibiting or damping waves or turbulence at the surface of the liquid are balls with or without holes, and Raschig rings, manufactured from porcelain, ceramic substances, glass or even lead, and having diameters approXimatei-y 5, l0, l or 2O mm. Even broken materials such as quartzite or materials having one or two restricted dimensions such as coils of wire, rods or wide mesh sieves may be used to advantage. The shape of the individual particles is immaterial as long as they have no sharp edges which might damage the threads if they do happen to come in contact therewith.

p As a result of the shape of the lling material, the receptacle can be filled with a great number of these particles, coils, rods, sieves, and the like, and yet contain a large quantity of treating liquid whichV can be heated if Vdesired and flow readily in the longitudinal direction of the receptacle even when the receptacle is substantially filled with the wave damping material. On the other hand, the material does restrain the movement of the liquid so strongly that it does not form waves as a result of the rapid movement of the threads through the bath.

It was determined that the' best results are attained when the receptacle is lied with the wave damping material to within a few mm., e. g., 2-5 mm. of the sheet of threads. The minimum distance is of course determined bythe type and size of the material.

it will be seen from the above that the greatest advantages of the invention canrbe attained in a system that is relatively simple although very effective for the purposes when the receptacles are properly lled with the'wave damping material. This material exerts a surprisingly strong iniluence on the liquid above the material so that no objectionable wave motion occurs therein.

In operation the sheet of threads is passed from one end of the container to the other in a substantially horizontal direction under a minimum of friction and with only a slight deiiection in a horizontal plane at the time the sheet enters the receptacle and aty the timeit leaves it.

The arrangement of the guiding bars may be varied to a wide degree as long as they act to maintain the sheet of threads in a straight line, i. e., without sagging, slightly below the surface of the bath liquid and slightly above the level of damping material. Moreover, the bars may be used as stripping guides which will accelerate and improve the aftertreatrnents, particularly with respect to the washing operation. By providing readily removable bars, the lower set acting as the sheet supportmay be put in position first and after the machine consisting of several similar receptacles has been initially threaded-up, the upper` set of bars may be fastened in place to gently urge the sheet of threads into the liquid at the surface thereof.

Fresh treating liquid is continuously admitted at the left of the receptacle and removed atthe right. T he frictional effect of the moving threads carries treating liquid to the right at the top of the receptacle, but no surface waves are encountered because the particles allow a steady return flow from right to left and damp out any uneven fluctuation in the rate of flow. A high degree of uniformity of treating conditions is thereby obtained.

The essential part of this invention resides in the elimination of surface waves from the receptacle by means of the material within the receptacle. The associated equipment of the thread treating system, therefore, does not affect the manner in which this invention improves the treating conditions except in the way in which they tend to produce wave motion.

In practice, receptacles can be used that are approximately l meter in width and 4 to 5 meters in length. The spacing between the thread may vary from 5 mm., for tine denier threads, to l5 mm. for the heavier deiner threads used for tire production.

The particular apparatus disclosed for defining the thread travel through the receptacle is peculiar to the present invention, although any similar system that is capable of maintaining the sheet of threads in a substantially straight line could be employed to equal advantage. The arrangement of bars shown in Figure 1, however, has been found to be especially suitable. Also, instead of a thread guiding edge at the thread-exit of the receptacle, a squeeze roll may be provided to return excess liquid back into the receptacle. Still further, rollers may be provided on each end whose speeds can be varied to give a desired stretch or relaxation to the threads during their passage through the receptacle.

Whereas, the foregoing description ofl the invention has been confined to a general aftertreatment of synthetic threads in one receptacle, it is to be understood that the same broad principle may be applied to similar receptacles modified to the extent only of adapting them to the required treatments.

What is claimedis: v

l. A process for the liquid after-treatment of a sheet of spacedv separate parallel synthetic threads that comprises, establishing a liquid treating bath having a substantial depth of liquid therein, passing said sheet of threads linearly and substantially horizontally through said bath immediately below the upper surface of the bath and immediately above the upper surface of a layer of substantial thickness of a wave damping material comprising a large number of inert solid bodies disposed in the liquid bath below the path of travel of said sheet of threads, thereby damping the surface wave formation that would otherwise occur as a result of the movement of the sheet of threads through the liquid bath.

2. A process for the continuous liquid treatment of a sheet of moving spaced separate parallel synthetic threads that comprises, passing the sheet linearly and substantially horizontally through a liquid treating bath of substantial depth While supporting the sheet at spaced areas, maintaining the moving sheet in a substantially horizontal plane just below the upper surface of the bath and just above the upper surface. of a mass of substantial thick- 5 ness of a wave damping material comprising a large number of inert solid bodies disposed in the liquid bath and extending upwardly to within a few millimeters of the moving sheet of threads, thereby damping the surface wave formation that would otherwise occur as a result of the movement of the sheet of threads through the liquid bath.

3. A process as defined in claim 2 4in which the inert solid bodies are Raschig rings.

References Cited in the le of this patent UNITED STATES PATENTS Greenwood Aug. 2, 1898 Maertensl Dec. 11, 19,00 Bosshard Sept. 6, 1932 Cohn Ian. 3, 1933 Harrison May 19, 1936 Cohn June 30, 1936 Nai Aug. 6, 1940 Gundelnger Aug. 12, 1941 Spangler Feb. 20, 1945 Spalding July 25, 1950 Costa Aug. 29, 1950 Kilham Dec. 5, 1950 Thomson et al May 29, 1951 Hoffman Mar. 4, 1952 FOREIGN PATENTS France Mar. 10, 1902 

1. A PROCESS FOR THE LIQUID AFTERTREATMENT OF A SHEET OF SPACED SEPARATE PARALLEL SYNTHETIC THREADS THAT COMPRISES, ESTABLISHING A LIQUID TREATING BATH HAVING A SUBSTANTIAL DEPTH OF LIQUID THEREIN, PASSING SAID SHEET OF THREADS LINEARLY AND SUBSTANTIALLY HORIZONTALLY THROUGH SAID BATH IMMEDIATELY BELOW THE UPPER SURFACE OF THE BATH AND IMMEDIATELY ABOVE THE UPPER SURFACE OF A LAYER OF SUBSTANTIAL THICKNESS OF A WAVE DAMPING MATERIAL COMPRISING A LARGE NUMBER OF INERT SOLID BODIES DISPOSED IN THE 